I wouldn't assume that the motor wants a spacer. Cheapest thing you could do is try it with no spacer. Especially if it is a mostly a street driven car. I have seen on the dyno where no spacer picks up the bottom end with little or no loss on the top end. I have also seen good gains mid and top with the right spacer with little or no loss to the bottom end. Don't count out the no spacer option unless you have already tried it. Keep in mind changing spacers can also change the air fuel ratio or the jet the motor wants. Generally but not always no spacer = less jet and spacer = more jet. It might be tough to sort out by seat of the pants.
